blocks|key|1463298|text|许多音频技术允许传入数据而不是声音文件。例如，AVAudioPlayer具有：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1463299|-initWithData:error:
Initializes+and+returns+an+audio+player+for+playing+a+designated+memory+buffer.

-+(id)initWithData:(NSData+*)data+error:(NSError+**)outError|code-block|syntax|javascript|1463300|但是，我不确定如何传递数据ptr，启动声音，然后通过传递其他数据ptr或重复相同的数据来保持其循环。|1463301|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Many of the audio technologies allow for data to be passed in instead of a sound file. AVAudioPlayer, for example, has:

<pre><code>-initWithData:error:
Initializes and returns an audio player for playing a designated memory buffer.

- (id)initWithData:(NSData *)data error:(NSError **)outError
</code></pre>

However, I am not sure how you would pass in a data ptr, start the sound, and then keeping it looping by passing in other data ptrs, or repeating the same, etc.

blocks|key|1248589|text|你想做什么，可能是为了设置一个AudioQueue。它允许您在回调中使用合成的音频数据填充缓冲区。可以将AudeioQueue设置为在新线程中运行，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1248590|#define+BUFFER_SIZE+16384
#define+BUFFER_COUNT+3
static+AudioQueueRef+audioQueue;
void+SetupAudioQueue()+{
++++OSStatus+err+=+noErr;
++++//+Setup+the+audio+device.
++++AudioStreamBasicDescription+deviceFormat;
++++deviceFormat.mSampleRate+=+44100;
++++deviceFormat.mFormatID+=+kAudioFormatLinearPCM;
++++deviceFormat.mFormatFlags+=+kLinearPCMFormatFlagIsSignedInteger;
++++deviceFormat.mBytesPerPacket+=+4;
++++deviceFormat.mFramesPerPacket+=+1;
++++deviceFormat.mBytesPerFrame+=+4;
++++deviceFormat.mChannelsPerFrame+=+2;
++++deviceFormat.mBitsPerChannel+=+16;
++++deviceFormat.mReserved+=+0;
++++//+Create+a+new+output+AudioQueue+for+the+device.
++++err+=+AudioQueueNewOutput(&deviceFormat,+AudioQueueCallback,+NULL,
++++++++++++++++++++++++++++++CFRunLoopGetCurrent(),+kCFRunLoopCommonModes,
++++++++++++++++++++++++++++++0,+&audioQueue);
++++//+Allocate+buffers+for+the+AudioQueue,+and+pre-fill+them.
++++for+(int+i+=+0;+i+<+BUFFER_COUNT;+%2B%2Bi)+{
++++++++AudioQueueBufferRef+mBuffer;
++++++++err+=+AudioQueueAllocateBuffer(audioQueue,+BUFFER_SIZE,+mBuffer);
++++++++if+(err+!=+noErr)+break;
++++++++AudioQueueCallback(NULL,+audioQueue,+mBuffer);
++++}
++++if+(err+==+noErr)+err+=+AudioQueueStart(audioQueue,+NULL);
++++if+(err+==+noErr)+CFRunLoopRun();
++}|code-block|syntax|javascript|1248591|当AudioQueue需要更多数据时，您的回调方法AudioQueueCallback将被调用。使用类似以下内容来实现：|1248592|void+AudioQueueCallback(void*+inUserData,+AudioQueueRef+inAQ,
++++++++++++++++++++++++AudioQueueBufferRef+inBuffer)+{
++++void*+pBuffer+=+inBuffer->mAudioData;
++++UInt32+bytes+=+inBuffer->mAudioDataBytesCapacity;
++++//+Write+max+<bytes>+bytes+of+audio+to+<pBuffer>
++++outBuffer->mAudioDataByteSize+=+actualNumberOfBytesWritten
++++err+=+AudioQueueEnqueueBuffer(audioQueue,+inBuffer,+0,+NULL);
}|1248593|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

What you want to do it probably to setup an AudioQueue. It allows you to fill a buffer with synthesized audio data in a callback. You would setup the AudeioQueue to run in a new thread as such:

<pre><code>#define BUFFER_SIZE 16384
#define BUFFER_COUNT 3
static AudioQueueRef audioQueue;
void SetupAudioQueue() {
 OSStatus err = noErr;
 // Setup the audio device.
 AudioStreamBasicDescription deviceFormat;
 deviceFormat.mSampleRate = 44100;
 deviceFormat.mFormatID = kAudioFormatLinearPCM;
 deviceFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger;
 deviceFormat.mBytesPerPacket = 4;
 deviceFormat.mFramesPerPacket = 1;
 deviceFormat.mBytesPerFrame = 4;
 deviceFormat.mChannelsPerFrame = 2;
 deviceFormat.mBitsPerChannel = 16;
 deviceFormat.mReserved = 0;
 // Create a new output AudioQueue for the device.
 err = AudioQueueNewOutput(&amp;deviceFormat, AudioQueueCallback, NULL,
 CFRunLoopGetCurrent(), kCFRunLoopCommonModes,
 0, &amp;audioQueue);
 // Allocate buffers for the AudioQueue, and pre-fill them.
 for (int i = 0; i &lt; BUFFER_COUNT; ++i) {
 AudioQueueBufferRef mBuffer;
 err = AudioQueueAllocateBuffer(audioQueue, BUFFER_SIZE, mBuffer);
 if (err != noErr) break;
 AudioQueueCallback(NULL, audioQueue, mBuffer);
 }
 if (err == noErr) err = AudioQueueStart(audioQueue, NULL);
 if (err == noErr) CFRunLoopRun();
 }
</code></pre>

You callback method AudioQueueCallback will then be called whenever the AudioQueue needs more data. Implement with something like:

<pre><code>void AudioQueueCallback(void* inUserData, AudioQueueRef inAQ,
 AudioQueueBufferRef inBuffer) {
 void* pBuffer = inBuffer-&gt;mAudioData;
 UInt32 bytes = inBuffer-&gt;mAudioDataBytesCapacity;
 // Write max &lt;bytes&gt; bytes of audio to &lt;pBuffer&gt;
 outBuffer-&gt;mAudioDataByteSize = actualNumberOfBytesWritten
 err = AudioQueueEnqueueBuffer(audioQueue, inBuffer, 0, NULL);
}
</code></pre>

blocks|key|1463408|text|戴维德·沃斯蒂与http://lists.apple.com/archives/coreaudio-api/2008/Dec/msg00173.html的链接不再有效，因为苹果名单似乎没有反应。以下是Google的缓存以保证完整性。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1463409|//
//++AudioUnitTestAppDelegate.m
//++AudioUnitTest
//
//++Created+by+Marc+Vaillant+on+11/25/08.
//++Copyright+__MyCompanyName__+2008.+All+rights+reserved.
//

#import+"AudioUnitTestAppDelegate.h"
#include+<AudioUnit/AudioUnit.h>
//#include+"MachTimer.hpp"
#include+<vector>
#include+<iostream>

using+namespace+std;

#define+kOutputBus+0
#define+kInputBus+1
#define+SAMPLE_RATE+44100

vector<int>+_pcm;
int+_index;

@implementation+AudioUnitTestAppDelegate

@synthesize+window;

void+generateTone(
++++++++++++++++vector<int>&+pcm,+
++++++++++++++++int+freq,+
++++++++++++++++double+lengthMS,+
++++++++++++++++int+sampleRate,+
++++++++++++++++double+riseTimeMS,+
++++++++++++++++double+gain)
{
++int+numSamples+=+((double)+sampleRate)+*+lengthMS+/+1000.;
++int+riseTimeSamples+=+((double)+sampleRate)+*+riseTimeMS+/+1000.;

++if(gain+>+1.)
++++gain+=+1.;
++if(gain+<+0.)
++++gain+=+0.;

++pcm.resize(numSamples);

++for(int+i+=+0;+i+<+numSamples;+%2B%2Bi)
++{
++++double+value+=+sin(2.+*+M_PI+*+freq+*+i+/+sampleRate);
++++if(i+<+riseTimeSamples)
++++++value+*=+sin(i+*+M_PI+/+(2.0+*+riseTimeSamples));
++++if(i+>+numSamples+-+riseTimeSamples+-+1)
++++++value+*=+sin(2.+*+M_PI+*+(i+-+(numSamples+-+riseTimeSamples)+%2B+riseTimeSamples)/+(4.+*+riseTimeSamples));

++++pcm[i]+=+(int)+(value+*+32500.0+*+gain);
++++pcm[i]+%2B=+(pcm[i]<<16);
++}

}

static+OSStatus+playbackCallback(void+*inRefCon,+
++++++++++++++++++++++++++++++++++AudioUnitRenderActionFlags+*ioActionFlags,+
++++++++++++++++++++++++++++++++++const+AudioTimeStamp+*inTimeStamp,+
++++++++++++++++++++++++++++++++++UInt32+inBusNumber,+
++++++++++++++++++++++++++++++++++UInt32+inNumberFrames,+
++++++++++++++++++++++++++++++++++AudioBufferList+*ioData)+
{++++
++++cout<<"index+=+"<<_index<<endl;
++++cout<<"numBuffers+=+"<<ioData->mNumberBuffers<<endl;

++++int+totalNumberOfSamples+=+_pcm.size();
++++for(UInt32+i+=+0;+i+<+ioData->mNumberBuffers;+%2B%2Bi)
++++{
++++++int+samplesLeft+=+totalNumberOfSamples+-+_index;
++++++int+numSamples+=+ioData->mBuffers[i].mDataByteSize+/+4;
++++++if(samplesLeft+>+0)
++++++{
++++++++if(samplesLeft+<+numSamples)
++++++++{
++++++++++memcpy(ioData->mBuffers[i].mData,+&_pcm[_index],+samplesLeft+*+4);
++++++++++_index+%2B=+samplesLeft;
++++++++++memset((char*)+ioData->mBuffers[i].mData+%2B+samplesLeft+*+4,+0,+(numSamples+-+samplesLeft)+*+4)+;
++++++++}
++++++++else
++++++++{
++++++++++memcpy(ioData->mBuffers[i].mData,+&_pcm[_index],+numSamples+*+4)+;
++++++++++_index+%2B=+numSamples;
++++++++}
++++++}
++++++else
++++++++memset(ioData->mBuffers[i].mData,+0,+ioData->mBuffers[i].mDataByteSize);
++++}

++++return+noErr;
}

-+(void)applicationDidFinishLaunching:(UIApplication+*)application+
{++++
++//generate+pcm+tone++freq+=+800,+duration+=+1s,+rise/fall+time+=+5ms

++generateTone(_pcm,+800,+1000,+SAMPLE_RATE,+5,+0.8);
++_index+=+0;

++OSStatus+status;
++AudioComponentInstance+audioUnit;

++//+Describe+audio+component
++AudioComponentDescription+desc;
++desc.componentType+=+kAudioUnitType_Output;
++desc.componentSubType+=+kAudioUnitSubType_RemoteIO;
++desc.componentFlags+=+0;
++desc.componentFlagsMask+=+0;
++desc.componentManufacturer+=+kAudioUnitManufacturer_Apple;

++//+Get+component
++AudioComponent+inputComponent+=+AudioComponentFindNext(NULL,+&desc);

++//+Get+audio+units
++status+=+AudioComponentInstanceNew(inputComponent,+&audioUnit);
++//checkStatus(status);

++UInt32+flag+=+1;
++//+Enable+IO+for+playback
++status+=+AudioUnitSetProperty(audioUnit,+
++++++++++++++++++kAudioOutputUnitProperty_EnableIO,+
++++++++++++++++++kAudioUnitScope_Output,+
++++++++++++++++++kOutputBus,
++++++++++++++++++&flag,+
++++++++++++++++++sizeof(flag));
++//checkStatus(status);

++//+Describe+format

++AudioStreamBasicDescription+audioFormat;
++audioFormat.mSampleRate+=+SAMPLE_RATE;
++audioFormat.mFormatID+=+kAudioFormatLinearPCM;
++audioFormat.mFormatFlags+=+kAudioFormatFlagIsSignedInteger+%7C+kAudioFormatFlagIsPacked;
++audioFormat.mFramesPerPacket+=+1;
++audioFormat.mChannelsPerFrame+=+2;
++audioFormat.mBitsPerChannel+=+16;
++audioFormat.mBytesPerPacket+=+4;
++audioFormat.mBytesPerFrame+=+4;

++//+Apply+format

++status+=+AudioUnitSetProperty(audioUnit,+
++++++++++++++++++kAudioUnitProperty_StreamFormat,+
++++++++++++++++++kAudioUnitScope_Input,+
++++++++++++++++++kOutputBus,+
++++++++++++++++++&audioFormat,+
++++++++++++++++++sizeof(audioFormat));
//++checkStatus(status);

++//+Set+output+callback
++AURenderCallbackStruct+callbackStruct;
++callbackStruct.inputProc+=+playbackCallback;
++callbackStruct.inputProcRefCon+=+self;
++status+=+AudioUnitSetProperty(audioUnit,+
++++++++++++++++++kAudioUnitProperty_SetRenderCallback,+
++++++++++++++++++kAudioUnitScope_Global,+
++++++++++++++++++kOutputBus,
++++++++++++++++++&callbackStruct,+
++++++++++++++++++sizeof(callbackStruct));

++//+Initialize
++status+=+AudioUnitInitialize(audioUnit);

++//+Start+playing

++status+=+AudioOutputUnitStart(audioUnit);

++[window+makeKeyAndVisible];
}


-+(void)dealloc+{
++++[window+release];
++++[super+dealloc];
}


@end|code-block|syntax|javascript|1463410|entityMap|0|LINK|mutability|MUTABLE|url|http://lists.apple.com/archives/coreaudio-api/2008/Dec/msg00173.html^0|8|1W|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Davide Vosti's link to <a href="http://lists.apple.com/archives/coreaudio-api/2008/Dec/msg00173.html" rel="nofollow">http://lists.apple.com/archives/coreaudio-api/2008/Dec/msg00173.html</a> no longer works, since Apple lists seem to be unresponsive. Here is Google's cache for completeness.

<pre><code>//
// AudioUnitTestAppDelegate.m
// AudioUnitTest
//
// Created by Marc Vaillant on 11/25/08.
// Copyright __MyCompanyName__ 2008. All rights reserved.
//

#import "AudioUnitTestAppDelegate.h"
#include &lt;AudioUnit/AudioUnit.h&gt;
//#include "MachTimer.hpp"
#include &lt;vector&gt;
#include &lt;iostream&gt;

using namespace std;

#define kOutputBus 0
#define kInputBus 1
#define SAMPLE_RATE 44100

vector&lt;int&gt; _pcm;
int _index;

@implementation AudioUnitTestAppDelegate

@synthesize window;

void generateTone(
 vector&lt;int&gt;&amp; pcm, 
 int freq, 
 double lengthMS, 
 int sampleRate, 
 double riseTimeMS, 
 double gain)
{
 int numSamples = ((double) sampleRate) * lengthMS / 1000.;
 int riseTimeSamples = ((double) sampleRate) * riseTimeMS / 1000.;

 if(gain &gt; 1.)
 gain = 1.;
 if(gain &lt; 0.)
 gain = 0.;

 pcm.resize(numSamples);

 for(int i = 0; i &lt; numSamples; ++i)
 {
 double value = sin(2. * M_PI * freq * i / sampleRate);
 if(i &lt; riseTimeSamples)
 value *= sin(i * M_PI / (2.0 * riseTimeSamples));
 if(i &gt; numSamples - riseTimeSamples - 1)
 value *= sin(2. * M_PI * (i - (numSamples - riseTimeSamples) + riseTimeSamples)/ (4. * riseTimeSamples));

 pcm[i] = (int) (value * 32500.0 * gain);
 pcm[i] += (pcm[i]&lt;&lt;16);
 }

}

static OSStatus playbackCallback(void *inRefCon, 
 AudioUnitRenderActionFlags *ioActionFlags, 
 const AudioTimeStamp *inTimeStamp, 
 UInt32 inBusNumber, 
 UInt32 inNumberFrames, 
 AudioBufferList *ioData) 
{ 
 cout&lt;&lt;"index = "&lt;&lt;_index&lt;&lt;endl;
 cout&lt;&lt;"numBuffers = "&lt;&lt;ioData-&gt;mNumberBuffers&lt;&lt;endl;

 int totalNumberOfSamples = _pcm.size();
 for(UInt32 i = 0; i &lt; ioData-&gt;mNumberBuffers; ++i)
 {
 int samplesLeft = totalNumberOfSamples - _index;
 int numSamples = ioData-&gt;mBuffers[i].mDataByteSize / 4;
 if(samplesLeft &gt; 0)
 {
 if(samplesLeft &lt; numSamples)
 {
 memcpy(ioData-&gt;mBuffers[i].mData, &amp;_pcm[_index], samplesLeft * 4);
 _index += samplesLeft;
 memset((char*) ioData-&gt;mBuffers[i].mData + samplesLeft * 4, 0, (numSamples - samplesLeft) * 4) ;
 }
 else
 {
 memcpy(ioData-&gt;mBuffers[i].mData, &amp;_pcm[_index], numSamples * 4) ;
 _index += numSamples;
 }
 }
 else
 memset(ioData-&gt;mBuffers[i].mData, 0, ioData-&gt;mBuffers[i].mDataByteSize);
 }

 return noErr;
}

- (void)applicationDidFinishLaunching:(UIApplication *)application 
{ 
 //generate pcm tone freq = 800, duration = 1s, rise/fall time = 5ms

 generateTone(_pcm, 800, 1000, SAMPLE_RATE, 5, 0.8);
 _index = 0;

 OSStatus status;
 AudioComponentInstance audioUnit;

 // Describe audio component
 AudioComponentDescription desc;
 desc.componentType = kAudioUnitType_Output;
 desc.componentSubType = kAudioUnitSubType_RemoteIO;
 desc.componentFlags = 0;
 desc.componentFlagsMask = 0;
 desc.componentManufacturer = kAudioUnitManufacturer_Apple;

 // Get component
 AudioComponent inputComponent = AudioComponentFindNext(NULL, &amp;desc);

 // Get audio units
 status = AudioComponentInstanceNew(inputComponent, &amp;audioUnit);
 //checkStatus(status);

 UInt32 flag = 1;
 // Enable IO for playback
 status = AudioUnitSetProperty(audioUnit, 
 kAudioOutputUnitProperty_EnableIO, 
 kAudioUnitScope_Output, 
 kOutputBus,
 &amp;flag, 
 sizeof(flag));
 //checkStatus(status);

 // Describe format

 AudioStreamBasicDescription audioFormat;
 audioFormat.mSampleRate = SAMPLE_RATE;
 audioFormat.mFormatID = kAudioFormatLinearPCM;
 audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
 audioFormat.mFramesPerPacket = 1;
 audioFormat.mChannelsPerFrame = 2;
 audioFormat.mBitsPerChannel = 16;
 audioFormat.mBytesPerPacket = 4;
 audioFormat.mBytesPerFrame = 4;

 // Apply format

 status = AudioUnitSetProperty(audioUnit, 
 kAudioUnitProperty_StreamFormat, 
 kAudioUnitScope_Input, 
 kOutputBus, 
 &amp;audioFormat, 
 sizeof(audioFormat));
// checkStatus(status);

 // Set output callback
 AURenderCallbackStruct callbackStruct;
 callbackStruct.inputProc = playbackCallback;
 callbackStruct.inputProcRefCon = self;
 status = AudioUnitSetProperty(audioUnit, 
 kAudioUnitProperty_SetRenderCallback, 
 kAudioUnitScope_Global, 
 kOutputBus,
 &amp;callbackStruct, 
 sizeof(callbackStruct));

 // Initialize
 status = AudioUnitInitialize(audioUnit);

 // Start playing

 status = AudioOutputUnitStart(audioUnit);

 [window makeKeyAndVisible];
}


- (void)dealloc {
 [window release];
 [super dealloc];
}


@end
</code></pre>

I'd like to play a synthesised sound in an iPhone. Instead of using a pre-recorded sound and using SystemSoundID to play an existing binary, I'd like to synthesise it. Partially, that's because I want to be able to play the sound continuously (e.g. when the user's finger is on the screen) instead of a one-off sound sample.

If I wanted to synthesise a Middle A+1 (A4) (440Hz), I can calculate a sine wave using sin(); what I don't know is how to arrange those bits into a packet which CoreAudio can then play. Most of the tutorials that exist on the net are concerned with simply playing existing binaries.

Can anyone help me with a simple synthesised sine sound wave at 440Hz?

How do I synthesize sounds with CoreAudio on iPhone/Mac

我想用iPhone播放合成的声音。与其使用预先录制的声音并使用SystemSoundID播放现有的二进制文件，我想要合成它。在某种程度上，这是因为我希望能够连续播放声音(例如，当用户的手指在屏幕上时)，而不是一次性的声音样本。如果我想合成一个中间A+1 (A4) (440 If )，我可以使用sin()计算一个正弦波；...

问如何在iPhone/Mac上用CoreAudio合成声音
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